The Income Tax department has decided to begin prosecution action against those having"substantial" amounts in their bank accounts in HSBC's Geneva branch.

The department has now written to the Finance Ministry to suggest a benchmark for funds held on the basis of which the IT department can initiate legal action for tax evasion and tax theft.

Top sources said a benchmark of about Rs five crore is being mulled for initiating court proceedings against those Indians whose names have figured on the secret list of HSBC Geneva, supplied to India by the French government.

All others below the benchmark amount, the sources said, could be penalised under I-T laws and the amount can be realised from them by way of raising a comprehensive tax demand.

The sources said a number of individuals or entities who have figured in these accounts, also searched and probed by the I-T department, held small balances ranging from few thousands to lakhs of rupees and, hence, a policy has to be made as to how many will be prosecuted and how many penalised under tax theft laws.

"A policy framework will be decided and action would be taken on a case-to-case basis," the sources said.

The I-T department, through the Finance Ministry, has already approached Swiss revenue authorities for banking data of certain individuals after investigations showed some of

them reportedly had other accounts under fictitious names.

The department has already begun a country-wide I-T assessment of those entities whose names have figured in these secret lists.

India had obtained data of over 700 HSBC accounts from French government channels last year.

According to the latest data, in 80 cases till now, the I-T department has detected undisclosed income of Rs 438 crore and taxes of Rs 135 crore have been realised so far.

The Finance Ministry had recently said that investigations are in progress with regard to these account holders days after activist Arvind Kejriwal accused it of inaction over black money allegedly stashed away in the HSBC Bank in Geneva.

The official statement had said that information was received in June last year by the government from its counterpart in France relating to certain bank accounts reportedly held by certain individuals and non-individuals in a foreign bank.